Does this make sense or am I over-thinking it?
Well, my son and I collect firearms - All are in firing condition. We shoot almost every firearm we purchase, (my wife has a Mosin I know will shoot but it was made in her birth year so she doesn't want to shoot it). We have, as I recall about 35 calibers. We have ammo for all of the firearms we own and reloading equipment for all. We also have bullet molds for most, with equipment to add gas checks and size/lube rifle rounds. At present we keep about 30K of rounds in our stash and supplies to reload most of them. It is nice to see a bargain on a caliber at a gun show and purchase it knowing we have a gun to shoot it in. We do buy mostly in bulk (ammo and supplies) so have purchased a lot of ammo at low cost in the last 20 years.
I guess for some folks, having just one caliber makes sense. I do not see it that way. I shoot a lot of different disciplines. Several calibers are needed to be able to do that. I have over 70 loads that I reload for 24 cartridges, plus shotgun. Some loads are for only one gun. Some guns share loads with others of the same caliber. It all depends on what load the gun shoots best. I have 11 different loads for 38 special. 8 loads for 44 mag. I only have 12 gauge shotguns, but I load several different loads for the 12. 22LR ammo is the same way. Some ammo may shoot great in a few guns, but other guns like other ammo.
I don't see any way to standardize on one cartridge or even one load for one cartridge. What I am shooting will determine what load I use.